The present invention relates to a method and apparatus for measuring the displacement of the free end of fixed structures such as buildings or offshore platforms used in the production of oil. The free end of structures which have a relatively small base in relation to their height are displaced either by wind forces, in the case of buildings, or wave and current action in the case of offshore platforms. It is desirable to know the actual displacement and the frequency of the displacement of these structures to provide more accurate information for designing the structures.
In the past, movement of the buildings has been determined by observing the building from a fixed position. While this method is satisfactory wherever a fixed reference is available, it obviously will not work on an offshore platform.
Inertial guidance systems are known that integrate acceleration measurements to obtain displacement measurements. This technique cannot be applied to measuring the displacement of structures having one fixed end and one free end because of the very low accelerations, velocity and displacement of these structures.